Changes in the incidence of cannabis-related disorders after the Cannabis Act and the COVID-19 pandemic in Québec, Canada

Abstract

Background: The Canadian Cannabis Act (CCA, implemented in October 2018) and the COVID-19 pandemic (April 2020) might have contributed to cannabis-related harms in Québec, known for its stringent cannabis legal framework. We explored changes in incidence rates of cannabis-related disorders (CRD) diagnoses associated with these events in Québec.

Methods: We utilized linked administrative health data to identify individuals aged 15 year+ newly diagnosed with CRD during hospitalizations, emergency, and outpatients clinics across Québec, from January 2010 and March 2022 (147 months). Interrupted time-series analyses (ITSA) assessed differences (as percentage changes) in sex- and age-standardized, and sex-stratified, monthly incidence rates (per 100,000 population) attributed to the CCA and the COVID-19 pandemic, compared to counterfactual scenarios where pre-events trends would continue unchanged.

Results: The overall monthly mean rates of incident diagnoses nearly doubled from the pre-CCA period (1.56 per 100,000 population) to the COVID-19 pandemic period (3.02 per 100,000 population). ITSA revealed no statistically significant level or slope changes between adjacent study periods, except for a decrease in the slope of incidence rates among males by 1.84 % (95 % CI -3.41 to -0.24) during the COVID-19 pandemic compared to the post-CCA period. During the post-CCA period, the trends of incidence rates in the general and male populations grew significantly by 1.22 % (95 % CI 0.08 to 2.35) and 1.44 % (0.04 to 2.84) per month, respectively. Similarly significant increases were observed for the general and female populations during the COVID-19 pandemic, with monthly rates rising by 1.43 % (95 % CI 0.75 to 2.12) and 1.75 % (95 % CI 0.13 to 3.37), respectively. These increases more than doubled pre-CCA rates.

Conclusions: The incidence rates of CRD diagnoses across Québec appears to have increased following the implementation of the CCA and during the COVID-19 pandemic. Our findings echo public health concerns regarding potential cannabis-related harms and are consistent with previous Canadian studies.

Keywords: Cannabis Act; Cannabis-related disorders; Interrupted time series; Quebec.